Conductive polymers such as polypyrrole and the like are known to have electrochemomechanical deformation, phenomena of expansion and contraction by electrochemical redox reaction. Recently, this electrochemomechanical deformation of conductive polymers has been attracting public attention, because this is expected to be applied for the use of artificial muscles, robot arms, artificial arms, actuators and the like and applications not only for smaller equipments such as for micro machines and the like, but also for larger machines have been attracting public attention as well.
As a process for producing conductive polymers, a process by electrochemical polymerization method is common. A common electrochemical polymerization method includes by adding monomer components such as pyrrole and the like in electrolytic solution, providing a working electrode and a counter electrode in this electrolyte, and applying voltage between the electrodes, thereby forming conductive polymers as films on the working electrode (e.g. see pages 70 to 73, “Conductive polymers” 8th edition by Naoya Ogata, published by Scientific K.K, Feb. 10, 1990”). Conductive polymers obtained by electrochemical polymerization can be subject to displacement such as expansion-contraction or bending by applying voltage to conductive polymers formed like films.
When elements which include conductive polymers manufactured by electrochemical polymerization (hereinafter called conductive polymer elements) are used as actuators in a driving part for uses of large sized equipments such as robot arms of industrial robots and the like, and artificial muscles such as artificial hands and the like, compared with elements for the uses of small sized actuators such as for micro machines and the like, it is necessary to make sizes of elements large enough to obtain larger amount of expansion-contraction or larger electrochemical stress. Therefore, in order to enlarge sizes of conductive polymer elements, it is necessary that conductive polymer films obtained by electrochemical polymerization are processed to be longer or thicker by piling up plural of films, or the like.
As conductive polymer elements with larger sizes, with a view to obtaining larger expansion and contraction in the length direction and in the height direction compared with conventional uses, longer conductive polymer elements compared with conventional conductive polymer elements are also used since they are sometimes used as driving parts, the use which requires enlarged conductive polymer elements in the length direction or in the height direction. Desirable electrochemical strain can be obtained by selecting the kinds of conductive polymers and dopants depending on the uses and by controlling the length of conductive polymer elements since deformation ratio of conductive polymer elements is determined by the kinds of conductive polymers and dopants which are included in conductive polymer elements.
However, in obtaining large electrochemical strain, there is a problem that, regarding the conductive polymer elements with selected kinds of conductive polymers and dopants, for example, satisfactory potential cannot be applied at the upper portion of elements since the conductivity of conductive polymers obtained by electrochemical polymerization is generally around 102 S/cm even when electrodes are provided on the whole bottom surface in the case where the conductive polymer elements enlarged in the direction of the columnar body height are used, and in the dedoped state, since conductivity further lowers, satisfactory potential cannot be applied at the upper portion of electrodes and when electrodes such as metal plates and the like are provided in the height direction, electrodes such as metal plates and the like inhibit the motion of conductive polymer elements, causing the problem of difficulty for said conductive polymer elements to expand and contract.
In order to solve the above problem, as a means to obtain large electrochemical strain of conductive polymer elements, one idea of pasting highly conductive metal films on surfaces of conductive polymer elements may be considered. However, since conductive polymer elements provided with said metal films on surfaces inhibit deformation since highly conductive metal films have little deformation property and these films cannot be applied to actuators which move in a linear manner by voltage application because displacement by electrochemical redox becomes bending but not expansion and contract. In addition, when conductive polymer elements provided with said metal films are applied to actuators which moves in a linear manner, a problem that metal films are separated from metal films due to repeated displacement and when metal films are firmly fixed to conductive polymer elements to conductive polymer elements with adhesives and the like, the problem that even bending motion is inhibited occurs. In addition, elements capable of uniformly applying electric charge over a whole element by connecting a lead to one point of a bottom surface of said elements are more advantageous since a composition of a element-driving device is not restricted.
Further, since large sized conductive polymer elements do not have high mechanical strength in conductive polymer elements, mechanical strength required for applications to robot arms such as industrial robots and the like, artificial muscles such as artificial hands which are the applications to large sizes may be not enough. Therefore, it is desirable to employ reinforcement means which improves mechanical strength of conductive polymer elements when large sized conductive polymer elements are used as practical uses.
Further, since conductive polymers are liable to be cut during the operation process because mechanical strength of conductive polymers themselves is not high, it is difficult to form desirable conductive polymer electrodes, that is, with an external diameter or width of less than 1 mm by processing such as cutting conductive polymer films obtained by electrochemical polymerization and the like in order to obtain small-sized conductive polymer elements represented by micro machines such as nano machines, catheters and the like. In addition, since conductive polymer elements are hard to be melted, production methods such as extrusion moldings, injection moldings and the like cannot be employed, the methods usually employed in producing thin lines such as wires or cylindrical resin mold products. For this reason, actuator elements which are driven to make expanding and contracting motion or to make bending motion by electrochemomechanical deformation of conductive polymers are not put into practical uses as small sized driving parts which include nano machines and micro machines. Therefore, in order to use for small sized elements represented by nano machines and micro machines, it is also desirable to obtain actuator elements which are driven to make expanding and contracting motion or to make bending motion by electrochemomechanical deformation of conductive polymers as small sized elements with external diameter or width of less than 1 mm.
In addition, since it is desirable that large sized actuator elements can produce uniform electrochemical stress in each portion of said actuator elements, it is desirable to uniformize amount of conductive polymers regarding each portion of actuator elements as a whole. Therefore, it is desirable to make further large actuator elements by using plural of actuator elements capable of being displaced for practical use such as expansion and contract or bending. It is necessary that each of plural actuator elements which compose one large sized actuator is obtained but it is desirable that a number of them are produced efficiently and easily in a short time.
It is the object of the present invention to provide elements capable of being displaced for practical use such as expansion and contract or bending even when conductive polymer elements are used as large sized actuator elements.